Homophymia pollubrum, Schlacher-Hoenlinger & Pisera & Hooper, 2005

Schlacher-Hoenlinger, Monika A., Pisera, Andrzej & Hooper, John N. A., 2005, Deep-sea “ lithistid ” assemblages from the Norfolk Ridge (New Caledonia), with description of seven new species and a new genus (Porifera, Demospongiae), Zoosystema 27 (4), pp. 649-698 : 686-688

Homophymia pollubrum n. sp.

( Figs 4B ; 18 ; 32 )

HOLOTYPE. — Kaimon-Maru seamount, Norfolk Ridge, 24°43’83”S, 168°09’34”E, 233-246 m, RV Alis, 22.VI.2001, Warén dredge, coll. T. Schlacher ( MNHN DCL 3906 , a fragment of the holotype in QM [G318659s).

ETYMOLOGY. — Named for the shallow bowl shape ( pollubrum, Greek for washbasin).

DESCRIPTION

Growth form

Known only from the holotype. Massive spherical sponge with a short, broad peduncle and a flattened upper surface and an axial cavity, which extends throughout the spherical part of the sponge and ends as a small opening as terminal extension at the flattened summit. The examined specimen is about 2.5 cm high, 3 cm wide and has a 2 cm broad base.

Colour

Beige in etoh.

Oscules

One large oscule at one side of the sponge (0.6 mm) and a small opening at the flattened summit of the spherical sponge (1 mm).

Texture

Hard.

Surface ornamentation

Rough with surface striations (subdermal canals).

Ectosomal skeleton

Ectosomal surface is composed of pseudophyllotriaenes, which are partially fused by their zygoses with neighbouring ectosomal megascleres and choanosomal desmas below the surface. Rhabdomes of the pseudophyllotriaenes, which are shorter than the cladomes, are orientated perpendicular to the surface. Amphiasters are very abundant in the ectosome.

Choanosomal skeleton

Dense network of highly irregularly branched desmas with root-like termini. Clones are smooth. Zygomes bear smooth mushroom-shaped tubercules which are tightly wrapped and composed of the sinuous interlocking fingers of the desmas termini. Heavy zygome development. Amphiasters are abundant and regularly dispersed throughout the choanosome. Microscleres are scattered throughout the choanosome.

Megascleres

Desmas are monocrepid, and highly irregularly branched with smooth clones and tightly wrapped, root-like termini. The latter bear numerous, mushroom-shaped tubercles. Adjacent desmas are heavily zygosed and build a complex skeletal network via entanglement of their extremities, which is aided by the sinuous interlocking fingers of the zygome termini: 400-500 µm/35-45µm.

Pseudophyllotriaenes: 395-541 µm in diameter; in other places 244-270 µm in diameter; rhabd shorter than diameter of the cladome 120- 150 long µm.

Microscleres

Amphiasters: 12.7-18.8 × 11.7-16.2 µm.

REMARKS

This species differs clearly from the type species Homophymia lamellosa in shape and spiculation. It resembles more closely H. stipitata Kelly, 2000 , in being semiglobular, but differs in having a deep narrow spongocoel and a very short and wide peduncle. It differs also from this species in having less branched pseudophyllotrienes which have wide clades. Amphiasters in both species are similar, but in H. pollubrum they are slightly larg- er, have longer rays and are less massive in appearance.

Family PHYMATELLIDAE Schrammen, 1910 DEFINITION. — Polymorphic lithistids with large, regular, usually smooth tetraclone desmas as choanosomal spicules and smooth ectosomal dichotriaenes; microscleres are amphiasters/streptasters (Pisera F Lévi 2002f).

Figures

FIG. 4. — A, Discodermia proliferans Lévi & Lévi, 1983; B, Homophymia pollubrum n. sp.; C, Reidispongia tuberculata n. sp.; D, R. coerulea Lévi & Lévi, 1988. Scale bars: 1 cm.

FIG. 18. — Homophymia pollubrum n. sp.; A, details of the outer surface with ectosomal pseudophyllotriaenes; B, outer surface of the choanosomal skeleton; C, choanosomal skeleton; D-F, details of desma terminal articulation. Scale bars: A, C, E, 200 µm; B, 1 mm; D, 100 µm; F, 10 µm.

FIG. 32. — Homophymia pollubrum n. sp.; A-D, amphiasters, E-G, ectosomal pseudophyllotriaenes. Scale bars: A-D, 5 µm; E-G, 100 µm.